But the headlines about the study did not always reflect that. Many, such as "Scientific Study Links Flammable Drinking Water to Fracking," pointed toward the fracturing process as a culprit. Even the press release accompanying the study was titled "Hydrofracking Changes Water Wells."

Confused? Many people are, even some in the thick of the debate.

The problem is that "fracking" means different things to different people.

People in the oil and gas industry commonly say "fracking" to describe just one part of the whole gas exploration and production process. Chemical-laced water and sand are blasted underground to break apart rock and release gas. Purists would say it is not really even part of "drilling" but actually the "completion" phase.

"Fracking and drilling are not the same thing," said University of Houston engineering professor Michael Economides, who consults for drillers on fracturing. "We drill wells. Then we frack."

But to many outsiders, particularly industry critics, fracking and drilling are the same thing. Advances in fracturing technology made possible the current shale gas drilling boom, so they have taken to lumping all shale gas production under the banner "fracking," deeming it a new form of natural gas drilling.

The study released this week, done by scientists at Duke University, suggested that gas drilling causes methane gas to leak into people's water and sometimes their homes (Greenwire, May 9). But methane contamination is not caused by injecting chemicals down the well. It is caused by bad well construction during drilling.

"The hot-button issue is fracking," said Robert Jackson, the Duke professor who authored the study, in an interview. But, he said, "I believe it's more about the drilling than the fracking."

Both drilling critics and supporters use the confusion to their advantage. The result is that the two sides often talk past one another when discussing the environmental consequences of oil and gas production from shale formations.

Drilling companies have repeatedly assured Congress, and whoever else asks, that there has never been a "proven" instance of hydraulic fracturing contaminating groundwater (E&ENews PM, May 6).

That denial infuriates critics who can point to numerous fines and penalties issued by regulators against shale drilling companies for contaminating drinking water with methane and for spilling toxic fracturing chemicals into streams near drill sites.

But by the definition of industry, along with most everyone who followed oil and gas issues before the current shale drilling boom, fracturing didn't cause those problems.

That is because the companies are saying, specifically, that no one has ever proven that hydraulic fracturing fluid rises up a mile or so from the production zone, through layers of rock, to pollute drinking water aquifers.

They rarely, if ever, clarify that regulators have repeatedly linked water contamination and other environmental problems to other aspects of drilling.

For example, a well blowout during fracturing last month in Pennsylvania, sent fluid to a nearby stream, threatening surface water, not groundwater (Greenwire, May 4). And a well-known contamination case in Dimock, Pa., involved methane -- not fracturing fluid -- in local water wells (Greenwire, Dec. 16, 2010).

Environmentalists and other industry critics consider this distinction to be nothing more than word games concocted by oil and gas lobbyists. Whatever you call it, they say, gas production is fouling air and water.

"When they confine their definition to the single moment of the underground fracturing -- a part of the process that has never been investigated -- they can legally deny the obvious," wrote Josh Fox, director of the anti-drilling documentary "Gasland," in a rebuttal to industry criticism of his film.

Spills and methane contamination fall under existing state and federal regulations. Fracturing, by contrast, received a specific exemption from the Safe Drinking Water Act from a Republican Congress and then-President George W. Bush in the 2005 energy bill.

Environmentalists and some congressional Democrats want to reverse that exemption under legislation called the "Fracturing Responsibility and Awareness of Chemicals Act," or FRAC Act.

The safety of the fracturing process itself has been challenged. But industry and regulators have dismissed them as unsubstantiated.